"HiMem.sys suddenly won't load XMS Memory"

HiMem.sys suddenly won't load XMS Memory so that Windows 98SE won't finish loading. There is no virus, memory chips are OK as are the hard drives. Debug reads the memory location OK, so HiMem must not like what it finds there.

I have already re-installed Windows...didn't help.
The Boot Log just stops at loading msmouse without giving any failure.

Could this be tied into Int 13 and EZ Drive? Dos seems to work just fine with no problem reading or writing to any of the drives. The computer is a PII, not used very often, and has been fine.